From 2af28ad897671a1c6a46d64b06ac1887c35ad7b5 Mon Sep 17 00:00:00 2001
From: Steven Schronk <steven@schronk.com>
Date: Tue, 15 Dec 2009 22:31:54 -0600
Subject: [PATCH] Advanced calculator now supports modulus.

---
 calc_adv.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 calc_adv.c

diff --git a/calc_adv.c b/calc_adv.c
new file mode 100644
index 0000000..daddccd
--- /dev/null
+++ b/calc_adv.c
@@ -0,0 +1,129 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+#define MAXOP 100
+#define NUMBER '0'
+#define MAXVAL 100
+#define BUFSIZE 100
+
+int getop(char[]);
+void push(double);
+double pop(void);
+
+int main()
+{
+	int type;
+	double op2;
+	char s[MAXOP];
+
+	while((type = getop(s)) != EOF)
+	{
+		switch(type)
+		{
+			case NUMBER:
+				push(atof(s));
+				break;
+			case '+':
+				push(pop() + pop());
+				break;
+			case '*':
+				push(pop() * pop());
+				break;
+			case '-':
+				op2 = pop();
+				push(pop() - op2);
+				break;
+			case '/':
+				op2 = pop();
+				if(op2 != 0.0)
+					push(pop() / op2);
+				else
+					printf("error: zero divisor\n");
+				break;
+			case '%':
+				op2 = pop();
+				if(op2 != 0.0)
+				{
+					push((int)(pop()) % (int)(op2));
+				} else {
+					printf("error: zero divisor\n");
+				}
+				break;
+			case '\n':
+				printf("\t%.8g\n", pop());
+				break;
+			default:
+				printf("error: unknown command %s\n", s);
+				break;
+		}
+	}
+	return 0;
+}
+
+int sp = 0;
+double val[MAXVAL];
+
+/* push f onto value stack */
+void push(double f)
+{
+	if(sp < MAXVAL)
+		val[sp++] = f;
+	else
+		printf("error: stack full\n");
+}
+
+
+/* pop and return top value from stack */
+double pop(void)
+{
+	if(sp > 0)
+		return val[--sp];
+	else
+	{
+		printf("error: stack empty\n");
+		return 0.0;
+	}
+}
+
+int getch(void);
+void ungetch(int);
+
+/* get next operator or numberic operand */
+int getop(char s[])
+{
+	int i, c;
+
+	while ((s[0] = c = getch()) == ' ' || c == '\t')
+		;
+	s[1] = '\0';
+	if(!isdigit(c) && c != '.')
+		return c;
+	i = 0;
+	if(isdigit(c))
+		while(isdigit(s[++i] = c = getch()))
+			;
+	if(c == '.')
+		while(isdigit(s[++i] = c = getch()))
+			;
+	s[i] = '\0';
+	if(c != EOF)
+		ungetch(c);
+	return NUMBER;
+}
+
+char buf[BUFSIZE];
+int bufp = 0;
+
+int getch(void)
+{
+	return (bufp > 0) ? buf[--bufp] : getchar();
+}
+
+void ungetch(int c)
+{
+	if(bufp >= BUFSIZE)
+		printf("ungetch: too many characters\n");
+	else
+		buf[bufp++] = c;
+}
-- 
2.11.4.GIT